STEAM 93 



EXAMPLE 2. The pressure in a steam boiler as shown by 

 the gauge is 87 Ib. per sq. in. What is the temperature of 

 the steam? 



SOLUTION. The absolute pressure is 87+14.7 = 101.7 Ib. 

 per sq. in. This pressure, in the Steam Table, lies between, 

 the values 100 and 105. 



for = 1051b., f = 331.13 

 for = 100 Ib.. * = 327.58 

 Difference, 5 Ib., 3.55 

 For 1 Ib. change of pressure, the difference in temperature 



3.55 



is = .71. From 100 Ib. to 101.7 Ib., the change of pres- 

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sure is 1.7 Ib., and the corresponding change of temperature 

 is .71X 1.7 = 1.207, or 1.21 as the values in the Steam 

 Table contain but two decimal places. For 101.7 Ib., therefore, 

 the temperature is 327.58 + 1.21 = 328.79. 



EXAMPLE 3. What is the pressure of steam at a temperature 

 of 285 P.? 



SOLUTION. From the Steam Table, 



for/ = 285.72, = 541b. 

 for / = 283.32, p = 52 Ib. 

 Difference, 2.40, 2 Ib. 



From t = 283.32 to / = 285, the increase of temperature 

 is 1.68. Now, since an increase of temperature of 2.40 gives 

 an increase of pressure of 2 Ib., the increase of 1.68 must give 



1.68 

 an increase of pressure of X2 lb. = 1.4 Ib. Hence, the 



required pressure is 52 lb. + 1.4 lb. = 53.4 Ib. 



EXAMPLE 4. Find, from the Steam Table, the total heat of 

 a pound of saturated steam at a pressure of 63 Ib. per sq. in., 

 gauge. 



SOLUTION. The absolute pressure is 63 + 14.7 = 77.7 Ib. per 

 sq. in. From the Steam Table, 



for p = 78 Ib., H = 1,176.5 B. T. U. 



for p = 76 Ib., H = 1.176.0 B. T. U. 



Difference, 2 Ib., .5 B. T. U. 



Difference, 1 Ib., .25 B. T. U. 



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